Self-Fealing Properties Of Microcapsule /LEDP Insulation Composite

Polyolefin materials are more used as the main components of various projects because of their excellent,unique performances and low cost.In the field of electrical insulation material,polyethylene cable can better meet the development needs of current power system,because of its various advantages.Thus,it has become an important skeleton of modern power grid,especially as the main carrier of urban power grid.In addition,the composite materials based on polyethylene show significant application advantages and are expected to become new electrical insulation material.However,minor defect,as the main damage form of polyolefin,can cause safety hazards to the operation of equipment.In the manufacturing,equipment and operation process of polyethylene cable,the operation and environmental factors will produce damages.This kind of damage is not only difficult to detect and repair,but also distort the electric field and degrade the material performance,thus significantly shorten its operation life and seriously threaten the safety of power supply.Therefore,it is necessary to study the polyethylene insulation material with self-healing ability to fundamentally extend the service life of the insulation material and improve the reliability of power grid.Based on the microcapsule self-healing system,this paper studied the self-healing microcapsule / LDPE insulation composite innovatively.Moreover,the mechanical,physicochemical,electrical and self-healing properties of the composite were analyzed from the aspects of theory,experiment and simulation.Besides,the effects of microcapsule on the properties of polyethylene and the self-healing performance of composite were studied.Furthermore,the changing rules of typical properties of composite and the behavior mechanism of self-healing ability were revealed.In addition,the problem of correlation analysis between damaged structure and electrical characteristics under self-healing ability was solved.This study not only helps to improve the mechanism analysis of self-healing material,but also provides guidance for the preparation of polyethylene insulation material with self-healing ability.In brief,this work provides a new way to improve the reliability of power grid,and can be widely used in other polyolefin materials,providing support for the development of new material.The main work of this paper is as follows:(1)According to the operation and application characteristics of polyethylene insulation material,the appropriate microcapsule system was selected,and the in-situ polymerization process was improved.Moreover,the corresponding test scheme was designed from the point of structure and performance requirements.The physical structure,chemical structure,thermal stability and micromechanical properties of UF /DCPD microcapsule were studied.Furthermore,the preparation method and performance characteristics of microcapsule system for insulation material were obtained,which laid a foundation for the follow-up study of insulation composite.(2)The preparation scheme of microcapsule / LDPE insulation composite was explored.Besides,the composites with different concentration were obtained by adjusting the melt blending method.The transverse and longitudinal structural characteristics of composite were studied.And the doping effect of microcapsule in the polyethylene matrix was analyzed.Moreover,the influence of the microcapsule on the doping effect was obtained.In brief,the structural characteristics of low concentration(≤ 1wt%)composite are proved to be superior,which provides guidance for the preparation of polyethylene insulation composite with self-healing ability.(3)Based on the application requirements of polyethylene insulation material,the important typical properties of composite materials were selected,and the reasonable test schemes were designed.The crystallization characteristics,thermal stability,mechanical tensile property,volume resistivity,AC breakdown strength and dielectric properties were studied.Moreover,the influence of microcapsule on the properties of polyethylene was analyzed.In addition,based on the characteristics of the microcapsule and the interface properties,the change mechanism of the typical properties was revealed.All in all,it is proved that the typical properties of low concentration(≤1wt%)composite are more suitable for the application requirements of polyethylene insulation material.(4)The typical damage types of PE cable were selected,and the corresponding self-healing test schemes were designed.The self-healing ability was verified from two aspects of mechanical damage and electrical damage.Moreover,the self-healing effect is quantified.The self-healing ability was evaluated by combining the damage structure of scratch and electrical tree with the self-healing effect of electrical properties such as breakdown strength and polarization characteristic.Futthermore,the suitable self-healing condition(about 60℃/30min)and the doping ratio of microcapsule(about1wt%)were studied,so that the self-healing efficiency could be maximized under the premise of maintaining the performances of polyethylene.(5)Combined with the micro behavior and macro characteristics,the self-healing characteristics and influencing factors of composite were analyzed.Besides,the self-healing behavior and mechanism were revealed by experimental analysis and simulation calculation.Finally,the application advantages and research value of 1wt%composite were proved.It not only has excellent typical properties,but also can repair the defective structure,restore the local electrical properties and reverse the degradation process of insulation material.